A hydrocracking method for heavy distillate oil

Abstract

The present invention discloses a hydrocracking method for heavy distillate oil. The method uses heavy distillate oil as a raw material for hydrocracking to produce chemical raw materials, and the chemical raw materials are ethylene raw materials and reforming raw materials. The method includes the steps of mixing heavy distillate oil with hydrogen and successively entering a hydrofining reaction zone, a first hydrocracking reaction zone, and a second hydrocracking reaction zone, and separating and fractionating the reaction effluent to obtain the chemical raw materials. This method can increase the production of high-quality ethylene cracking feedstock while improving the quality of heavy naphtha as a catalytic reforming feedstock.

Description

Technical Field

[0001] The present invention belongs to the field of hydrocarbon oil hydrocracking, and particularly relates to a hydrocracking method for heavy distillate oil. Background Art

[0002] In recent years, the oil reserves and production in American countries such as the United States, Canada, and Venezuela in the Western Hemisphere have increased significantly. These countries are gradually becoming emerging hotspots for global oil and gas exploration and development after the Middle East. The global oil consumption center and the refinery development center have further shifted to countries in the Eastern Hemisphere, and the crude oil resource supply has become further tightened. The development of unconventional oil and gas resources such as shale gas and shale oil has become a hotspot. At the same time, a series of new trends have emerged in the development pattern of the world refining industry: the trend of crude oil becoming heavier and inferior is obvious, the processing difficulty of heavy oil has increased, and the heavy oil deep processing technology has mainly made progress in aspects such as technology optimization and catalyst upgrading; the technology for refineries to increase the production of chemical raw materials such as low-carbon olefins and aromatics has developed rapidly along with the accelerated integration strategy of refining and chemical industries; alternative energy technologies have received high attention and entered the stage of large-scale industrial application.

[0003] The ethylene industry is the core of the petrochemical industry. Ethylene products account for more than 75% of petrochemical products and are one of the important indicators to measure the petrochemical development level of a country. Therefore, improving the production capacity of ethylene is an important way for petrochemical technology and product innovation. Generally speaking, the ethylene cracking feedstock structure in China is still relatively heavy. The proportion of liquid feedstocks such as naphtha in the ethylene cracking feedstock is relatively high, while the proportion of light hydrocarbons is relatively low. This results in the lack of international competitiveness in the cost of producing ethylene by steam cracking in China. Therefore, further optimizing the feedstock structure, deeply exploring the potential for integrated efficiency improvement, and increasing the proportion of light and low-grade feedstocks in the ethylene cracking feedstock are still important tasks for Chinese enterprises producing ethylene by steam cracking to reduce the production cost of olefins. The hydrocracking technology has the characteristics of strong feedstock adaptability, large flexibility in production operation and product scheme, and good product quality. It can directly convert various heavy and inferior feeds into high-quality jet fuel, diesel, lubricating oil base stock, chemical naphtha, and ethylene feedstock for steam cracking of tail oil. It has become one of the most important heavy oil deep processing processes in modern refining and petrochemical industries and has been increasingly widely used at home and abroad. With the current reduction in the demand for the fuel oil market in China, converting the maximum amount of heavy distillate oil fraction into high-quality chemical raw materials has become a beneficial technical path for refining enterprises to optimize product structure and improve economic benefits.

[0004] CN201580070326.4 discloses a method for preparing LPG and BTX, comprising: a) subjecting a mixed hydrocarbon stream to a first hydrocracking in the presence of a first hydrocracking catalyst to prepare a first hydrocracking product stream; b) separating the first hydrocracking product stream to provide at least one light hydrocarbon stream comprising at least C2 and C3 hydrocarbons, an intermediate hydrocarbon stream composed of C4 and / or C5 hydrocarbons, and a heavy hydrocarbon stream comprising at least C6+ hydrocarbons, and c) subjecting the heavy hydrocarbon stream to a second hydrocracking in the presence of a second hydrocracking catalyst to prepare a second hydrocracking product stream comprising BTX, wherein the second hydrocracking is more severe than the first hydrocracking, d) wherein at least part of the intermediate hydrocarbon stream is subjected to C4 hydrocracking in the presence of a C4 hydrocracking catalyst to prepare a C4 hydrocracking product stream, and the C4 hydrocracking is optimized for converting C4 hydrocarbons into C3 hydrocarbons.

[0005] CN201480037272.7 discloses a method for producing light olefin hydrocarbon compounds from a hydrocarbon feedstock, comprising the following steps: (a) feeding the hydrocarbon feedstock to a reaction zone for ring opening; (b) separating the reaction product produced by the reaction zone into an overhead stream and a side stream; (c) feeding the side stream from (b) to a gasoline hydrocracker (GHC) unit; (d) separating the reaction product of the GHC in step (c) into an overhead stream comprising hydrogen, methane, ethane and liquefied petroleum gas and a stream comprising aromatic hydrocarbon compounds and a small amount of hydrogen and non-aromatic hydrocarbon compounds; (e) feeding the overhead stream from the gasoline hydrocracker (GHC) unit to a steam cracker unit.

[0006] The above methods are mainly used for producing LPG and BTX. At the same time, when producing ethylene feedstock, the content of normal paraffins in the ethylene feedstock is low, which will also result in a low yield of trienes in the steam cracking to ethylene unit. Therefore, it is of great significance to develop a hydrocracking method suitable for producing high-quality chemical raw materials from heavy distillate oil. Summary of the Invention

[0007] Aiming at the problems existing in the prior art, the object of the present invention is to provide a heavy distillate oil hydrocracking method. This method uses heavy distillate oil as a raw material for hydrocracking to produce chemical raw materials, which can increase the production of high-quality ethylene cracking feedstock while improving the quality of heavy naphtha as a catalytic reforming feedstock.

[0008] The present invention provides a heavy distillate oil hydrocracking method, which uses heavy distillate oil as a raw material for hydrocracking to produce chemical raw materials, and the chemical raw materials are ethylene feedstock and reforming feedstock. Wherein, the method comprises:

[0009] (1) The heavy distillate oil is mixed with hydrogen and enters the hydrofining reaction zone, and then gas-liquid separation is carried out to obtain a gas-phase stream and a liquid-phase stream; the nitrogen content in the liquid-phase stream described in step (1) is controlled to be 50 mg / kg to 100 mg / kg;

[0010] (2) In the presence of hydrogen, the liquid-phase stream obtained in step (1) enters the first hydrocracking reaction zone, and the n-alkanes in the heavy distillate oil raw material are selectively cracked to obtain a first hydrocracking product; wherein, in the first hydrocracking product, the mass content of C7 + n-alkanes is controlled to be below 3.0%.

[0011] (3) In the presence of hydrogen, the first hydrocracking product enters the second hydrocracking reaction zone to obtain a second hydrocracking product containing monocyclic cyclic hydrocarbons;

[0012] (4) The second hydrocracking product is separated and fractionated to obtain a gas fraction, light naphtha, heavy naphtha and tail oil.

[0013] According to the present invention, the gas-phase stream obtained in step (1) is input to the hydrofining reaction zone for recycling.

[0014] According to the present invention, the nitrogen content in the liquid-phase stream described in step (1) is controlled to be 60 mg / kg to 80 mg / kg.

[0015] According to the present invention, the hydrofining reaction zone of step (1) is filled with a hydrofining catalyst. The hydrofining catalyst described in step (1) can adopt a conventional hydrofining catalyst, which is mainly used for hydrodesulfurization, nitrogen and other impurities. The hydrofining catalyst includes a carrier and a hydrogenation active metal, wherein the carrier is an inorganic refractory oxide, generally selected from one or more of alumina, amorphous silica-alumina, silica or titanium oxide, etc.; the hydrogenation active metal includes Group VIB and / or Group VIII metal components. Preferably, in the hydrofining catalyst, Group VIB is preferably selected from tungsten and / or molybdenum, and its content in the catalyst based on the mass of the oxide is 10% to 50%, preferably 20% to 30%; Group VIII is preferably selected from nickel and / or cobalt, and its content in the catalyst based on the mass of the oxide is 2% to 10%, preferably 3% to 8%; the content of the carrier is 42% to 88%, preferably 62% to 77%.

[0016] According to the present invention, the chemical raw materials mainly include ethylene raw materials and reforming raw materials. The chemical raw materials include ethane, propane, butane, light naphtha, and may also include heavy naphtha. Among them, heavy naphtha is used as a reforming raw material to produce BTX, and ethane, propane, butane and light naphtha are used as ethylene raw materials to produce light olefins, such as producing ethylene as a steam cracking raw material, and propane and butane can also be directly dehydrogenated to produce propylene and butene. Among them, light olefins refer to olefins with four or less carbon atoms, especially ethylene, propylene and butadiene.

[0017] According to the present invention, in the heavy distillate oil described in step (1), the mass content of cyclic hydrocarbons is 40% to 90%, and the cyclic hydrocarbons are the sum of naphthenes and aromatics. In the heavy distillate oil, the mass content of normal paraffins is 5% to 50%, preferably 10% to 30%. The heavy distillate oil is at least one of coal tar and shale oil. The distillation range of the heavy distillate oil is generally 100°C to 750°C; the density is generally 0.88 g / cm 3 ~1.20 g / cm 3 ; the nitrogen content is generally 0.6 wt% to 2.0 wt%, preferably 0.8 wt% to 1.5 wt%; the oxygen content is generally 0.5 wt% to 1.5 wt%, preferably 0.6 wt% to 1.0 wt%.

[0018] According to the present invention, in the obtained chemical raw materials, based on the total mass of ethane, propane, butane and light naphtha, the normal paraffins account for 50% to 70%, preferably 54% to 70%. Based on the total mass of ethane, propane, butane and light naphtha, after entering the steam cracking to ethylene unit, the yield of trienes (including ethylene, propylene and butadiene) reaches more than 50%, and further can reach 50% to 60%.

[0019] According to the present invention, the reaction conditions in the hydrofining reaction zone in step (1) are as follows: the reaction pressure is 16 to 22 MPa.

[0020] According to the present invention, the reaction conditions in the hydrofining reaction zone in step (1) are as follows: the average reaction temperature is 250 to 450°C, preferably 300 to 400°C; the liquid hourly space velocity is 0.1 to 15.0 h -1 , preferably 0.5 to 5.0 h -1 ; the hydrogen-oil volume ratio is 100:1 to 2500:1, preferably 400:1 to 2000:1.

[0021] According to the present invention, preferably, in step (2), the mass content of C7 + normal paraffins is controlled at 1 wt% to 3 wt%.

[0022] According to the present invention, in the first hydrocracking product of step (2), the ratio of the mass of C6-C8 monocyclic cyclic hydrocarbons to the total mass of cyclic hydrocarbons in the raw material is 0.15 to 0.35, preferably 0.25 to 0.34. The raw material is the heavy distillate oil.

[0023] According to the present invention, in step (2), the first hydrocracking reaction zone is filled with a first hydrocracking catalyst. The first hydrocracking catalyst can be one or more catalysts. In step (2), the first hydrocracking catalyst comprises an active metal component and a support; the support comprises a molecular sieve having selective cracking of normal paraffins, preferably selected from one or more of ZSM-5 molecular sieve, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35 and ZSM-38 molecular sieves, preferably ZSM-5 molecular sieve. The SiO2 / Al2O3 molar ratio of the ZSM-5 is 20 to 60. The support may further comprise a binder. Preferably, the binder is alumina. The active metal component comprises at least one of metals of Group VIB and Group VIII, the metal of Group VIB is preferably molybdenum and / or tungsten, and the metal of Group VIII is preferably cobalt and / or nickel.

[0024] According to the present invention, in step (2), preferably, in the first hydrocracking catalyst, based on the weight of the catalyst, the content of the metal of Group VIB (calculated as the oxide) is 5.0% to 15.0%, the content of the metal of Group VIII (calculated as the oxide) is 2.0% to 5.0%, and the content of the support is 80.0% to 93.0%.

[0025] According to the present invention, in step (2), preferably, in the support of the first hydrocracking catalyst, based on the weight of the support, the content of the binder is 8% to 60%, and the content of the molecular sieve is 40% to 92%.

[0026] According to the present invention, in step (2), the specific surface area of the first hydrocracking catalyst is 200 to 400 m 2 / g, and the pore volume is 0.25 to 0.45 mL / g.

[0027] According to the present invention, the preparation method of the first hydrocracking catalyst in step (2) can be prepared according to the conventional methods in the art. The preparation method comprises the preparation of the support and the loading of the active metal component, and the preparation process of the support is as follows: the shape-selective cracking molecular sieve and the binder are mechanically mixed, shaped, and then dried and calcined to make the catalyst support. The drying and calcination of the support can adopt conventional conditions. The conditions for drying are: drying at 100 °C to 150 °C for 1 to 12 hours. The conditions for calcination are: calcining at 450 °C to 550 °C for 2.5 to 6.0 hours.

[0028] According to the present invention, in step (2), in the preparation method of the first hydrocracking catalyst, the method for loading the active metal component is a conventional method, such as kneading method, impregnation method, etc., and the impregnation method is preferred. The impregnation method can be saturated impregnation method, excess impregnation method or complex impregnation method, that is, impregnating the catalyst support with a solution containing the required active component, and then drying and calcining to obtain the first hydrocracking catalyst. The conditions for the drying are: drying at 100°C to 150°C for 1 to 12 hours. The conditions for the calcining are: calcining at 450°C to 550°C for 2.5 to 6.0 hours.

[0029] According to the present invention, in step (2), the reaction conditions in the first hydrocracking reaction zone are as follows: the reaction pressure is 16 to 22 MPa.

[0030] According to the present invention, in step (2), the reaction conditions in the first hydrocracking reaction zone are as follows: the average reaction temperature is 250 to 450°C, preferably 300 to 400°C; the liquid hourly space velocity is 0.1 to 15.0 h -1 , preferably 1.0 to 5.0 h -1 ; the hydrogen-oil volume ratio is 100:1 to 2500:1, preferably 400:1 to 2000:1.

[0031] According to the present invention, in step (3), the second hydrocracking reaction zone is filled with a second hydrocracking catalyst. The second hydrocracking catalyst can be one or more catalysts. In step (3), the second hydrocracking catalyst has the functions of ring opening cracking of polycyclic cyclic hydrocarbons, selectively cracking the side chains of isoparaffins or cyclic hydrocarbons and retaining monocyclic cyclic hydrocarbons. The second hydrocracking catalyst includes a cracking component, a hydrogenation component and a binder. The second hydrocracking catalyst can be a commercially available product or prepared according to the prior art. The hydrogenation component is at least one of a metal, a metal oxide and a metal sulfide of the active metal component; the active metal component includes Group VIB and / or Group VIII metals; the active metal component is more preferably at least one of iron, chromium, molybdenum, tungsten, cobalt and nickel. In the second hydrocracking catalyst, the binder is alumina and / or silica; the cracking component includes an acidic molecular sieve, preferably at least one of Beta molecular sieve and Y molecular sieve.

[0032] According to the present invention, preferably, in step (3), the second hydrocracking reaction zone is filled with a catalyst with Y molecular sieve as the cracking component and a catalyst with Beta molecular sieve as the cracking component in sequence along the direction of the material flow; preferably, the volume ratio of the catalyst with Y molecular sieve as the cracking component to the catalyst with Beta molecular sieve as the cracking component is 1:1 to 1:5, preferably 1:2 to 1:4.

[0033] According to the present invention, in step (3), for the second hydrocracking catalyst, based on the weight of the second hydrocracking catalyst, the content of the hydrogenation component in terms of oxide is 5 wt% to 40 wt%, preferably 10 wt% to 20 wt%; the content of the cracking component is 20 wt% to 80 wt%, preferably 30 wt% to 70 wt%; the content of the binder is 5 wt% to 75 wt%, preferably 10 wt% to 50 wt%.

[0034] According to the present invention, in step (3), the preparation method of the second hydrocracking catalyst can be prepared according to the conventional methods in the art. The preparation method includes the preparation of the support and the loading of the hydrogenation component. The process of preparing the support is as follows: mechanically mix the cracking component and the binder, shape, and then dry and calcine to make the catalyst support. The drying and calcining of the support can adopt conventional conditions. The conditions for drying are: drying at 100°C to 150°C for 1 to 12 hours. The conditions for calcining are: calcining at 450°C to 550°C for 2.5 to 6.0 hours.

[0035] According to the present invention, in step (3), in the preparation method of the second hydrocracking catalyst, the method for loading the hydrogenation component is a conventional method, such as the kneading method, the impregnation method, etc., preferably the impregnation method. The impregnation method can be the saturated impregnation method, the excess impregnation method or the complex impregnation method, that is, impregnate the catalyst support with a solution containing the required hydrogenation component, and then dry and calcine to obtain the second hydrocracking catalyst. The conditions for drying are: drying at 100°C to 150°C for 1 to 12 hours. The conditions for calcining are: calcining at 450°C to 550°C for 2.5 to 6.0 hours.

[0036] According to the present invention, in step (3), the reaction conditions in the second hydrocracking reaction zone are as follows: the reaction pressure is 16 to 22 MPa.

[0037] According to the present invention, in step (3), the reaction conditions for the second hydrocracking reaction are as follows: the average reaction temperature is 250 to 450°C, preferably 300 to 400°C; the liquid hourly space velocity is 0.1 to 15.0 h -1 , preferably 1.0 to 5.0 h -1 ; the hydrogen-oil volume ratio is 100:1 to 2500:1, preferably 400:1 to 2000:1.

[0038] According to the present invention, preferably, the hydrotreating reaction zone, the first hydrocracking reaction zone and the second hydrocracking reaction zone adopt the same pressure.

[0039] According to the present invention, preferably, the effluent from the second hydrocracking reaction in step (3) is subjected to supplementary hydrotreating. The supplementary hydrotreating can be to load a hydrotreating catalyst at the bottom of the second hydrocracking reaction zone, or it can enter a separate hydrotreating reaction zone.

[0040] According to the present invention, preferably, the effluent from the second hydrocracking reaction in step (3) can also directly enter the fractionation system, and the separated heavy naphtha component can be subjected to additional hydrofining.

[0041] According to the present invention, the tail oil obtained in step (4) can be circulated to the first hydrocracking reaction zone in step (2), and / or circulated to the second hydrocracking reaction zone in step (3).

[0042] Compared with the prior art, the present invention has the following beneficial technical effects:

[0043] (1) In the heavy distillate oil hydrocracking method of the present invention, the heavy distillate oil is mixed with hydrogen and enters the hydrofining reaction zone, and the nitrogen content in the liquid phase product is controlled, which is conducive to controlling the appropriate refining reaction temperature and preventing the catalyst from being rapidly deactivated due to excessively high refining reaction temperature. Then, the feedstock and hydrogen enter the first hydrocracking reaction zone, mainly to selectively crack the normal alkanes and the long straight-chain isoalkanes and cycloalkanes containing long straight-chain hydrocarbons in the feedstock to generate small molecular normal alkanes, so that the C7 + The content of normal alkanes is below 3%. The effluent from the first hydrocracking reaction enters the second hydrocracking reaction zone, which mainly performs ring-opening cracking of polycyclic cyclic hydrocarbons and retains monocyclic cyclic hydrocarbons and further breaks the side chains of each hydrocarbon to generate small molecular hydrocarbons. In this way, a large amount of chain alkanes in the raw material can be converted into gas and light naphtha components, that is, they are enriched in the low-carbon olefin raw material, while monocyclic cyclic hydrocarbons are retained in the heavy naphtha fraction, that is, they are enriched in the reforming raw material. Through simple distillation, efficient separation of chain alkanes and cyclic hydrocarbons can be achieved, increasing the production of high-quality ethylene cracking feed while improving the quality of heavy naphtha as catalytic reforming feed.

[0044] Petroleum hydrocarbons have a complex composition, mainly including chain alkanes, cycloalkanes and aromatics, while high-quality ethylene raw materials are small molecular normal alkanes, and reforming raw materials are monocyclic cycloalkanes and aromatics. The inventors have found through research that the technical scheme of the present invention can generate small molecular normal alkanes with high selectivity, thereby achieving efficient enrichment of small molecular normal alkanes in low-carbon olefin raw materials, while retaining monocyclic cyclic hydrocarbons in heavy naphtha as much as possible to achieve efficient enrichment of high-quality reforming raw materials, so as to achieve the purpose of greatly improving the yield of chemical raw materials (i.e., low-carbon olefin raw materials and reforming raw materials) and the quality of low-carbon olefin raw materials and reforming raw materials, thereby completing the present invention.

[0045] (2) The content of monocyclic cyclic hydrocarbons in the heavy naphtha obtained by the method of the present invention is high. As the feedstock for the catalytic reforming unit, the alkane cyclization and dehydrogenation unit in the catalytic reforming unit can be cancelled, which can greatly reduce the investment and energy consumption of the catalytic reforming unit. At the same time, since the hydrocracking reaction follows the carbocation reaction mechanism, the side chain breaking reaction of cyclic hydrocarbons with more than C9 can be selectively realized, so that the C6-C8 cyclic hydrocarbons in the product have a higher enrichment degree, and the BTX yield can be greatly increased after catalytic reforming and aromatics extraction.

[0046] (3) The present invention selectively converts the alkanes in the heavy distillate oil into small molecule alkanes. This process will consume a certain amount of hydrogen, but the light hydrocarbons also have a high hydrogen yield as the raw material for the ethylene unit. The lower the carbon number, the higher the hydrogen yield. Therefore, most of the hydrogen consumed in the hydrogenation process can be recovered after passing through the ethylene unit. At the same time, the light hydrocarbons as the ethylene raw material can greatly increase the yields of ethylene, propylene and butadiene, and extend the cleaning cycle of the ethylene unit, significantly improving the economic benefits of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is a process flow schematic diagram of Examples 1-4 of the present invention;

[0048] MAIN REFERENCE NUMERAL DESCRIPTION:

[0049] 1 - heavy distillate oil, 2 - hydrogen, 3 - hydrofining reaction zone, 4 - hydrofining reaction effluent, 5 - separator, 6 - hydrogen-rich gas in the gas-phase stream, 7 - liquid-phase stream, 8 - first hydrocracking reaction zone, 9 - first hydrocracking reaction effluent, 10 - second hydrocracking reaction zone, 11 - second hydrocracking reaction effluent, 12 - separator, 13 - hydrogen-rich gas in the gas-phase stream, 14 - liquid-phase stream, 15 - fractionating tower, 16 - gas fraction, 17 - light naphtha, 18 - heavy naphtha, 19 - tail oil. DETAILED DESCRIPTION OF THE INVENTION

[0050] The functions and effects of the present invention will be further described below through examples, but the following examples do not limit the method of the present invention.

[0051] In the present invention, unless otherwise specified, % are all mass fractions.

[0052] The overall volume space velocity in the examples and comparative examples is the ratio of the fresh feed volume to the total volume of the catalyst.

[0053] In the present invention, as Figure 1As shown, heavy distillate oil 1 is mixed with hydrogen gas 2 and enters the hydrofining reaction zone 3. The hydrofining reaction effluent 4 enters the separator 5. The hydrogen-rich gas 6 separated is recycled for use. The liquid-phase stream 7 is mixed with hydrogen gas 2 and enters the first hydrocracking reaction zone 8 for hydrocracking reaction. The first hydrocracking reaction effluent 9 enters the second hydrocracking reaction zone 10 for hydrocracking reaction. The second hydrocracking reaction effluent 11 enters the separator 12. The hydrogen-rich gas 13 separated is recycled for use. The liquid 14 enters the fractionating tower 15, and gas 16, light naphtha 17, heavy naphtha 18, and tail oil 19 are separated. The tail oil 19 is recycled to the upstream of the reaction stream in the second hydrocracking reaction zone 10.

[0054] In the present invention, each example of the hydrofining catalyst is denoted by Cat-D. The hydrofining catalyst is prepared by a conventional active metal saturation impregnation method. The physicochemical properties of the obtained catalyst are shown in Table 2.

[0055] In the present invention, each example of the first hydrocracking catalyst is denoted by Cat-A plus a number, such as Cat-A1, Cat-A2, Cat-A3. The first hydrocracking catalyst is prepared by a conventional active metal saturation impregnation method. The physicochemical properties of the obtained catalyst are shown in Table 1.

[0056] In the present invention, each example of the second hydrocracking catalyst is denoted by Cat-B plus a number, such as Cat-B1, Cat-B2. The physicochemical properties of the catalyst are shown in Table 2. Each example of the second hydrocracking catalyst is prepared by a conventional active metal saturation impregnation method. Among them, the properties of the Beta zeolite used in Cat-B1 are as follows: the SiO2 / Al2O3 molar ratio is 30, the specific surface area is 350 m 2 / g, and the pore volume is 0.32 cm 3 / g. The properties of the Y zeolite used in Cat-B2 are as follows: the SiO2 / Al2O3 molar ratio is 15, the specific surface area is 400 m 2 / g, and the pore volume is 0.30 cm 3 / g. The physicochemical properties of the obtained catalyst are shown in Table 2.

[0057] In the present invention, each example uses a heavy distillate oil raw material, and its main properties are shown in Table 4.

[0058] In the present invention, in Examples 1 to 3, Cat-B2 and Cat-B1 are successively loaded in the second hydrocracking reaction zone along the material flow direction.

[0059] In the present invention, the ethylene raw material in each example refers to ethane, propane, butane, and light naphtha obtained in the product. Ethane, propane, butane, and light naphtha can be directly used as raw materials for steam cracking to produce ethylene.

[0060] In the present invention, the light naphtha has a distillation range of liquid components less than 60°C, the heavy naphtha has a distillation range of 60 - 175°C, and the tail oil has a distillation range of components greater than 175°C.

[0061] In the present invention, the yield of ethylene feedstock refers to the mass ratio of ethane, propane, butane, and light naphtha in the hydrocracking product to the fresh hydrocracking feedstock (heavy distillate oil), and the yield of heavy naphtha refers to the mass ratio of heavy naphtha in the hydrocracking product to the fresh hydrocracking feedstock.

[0062] Examples 1 - 4

[0063] The hydrocracking method adopts the following Figure 1 process, including:

[0064] (1) The heavy distillate oil is mixed with hydrogen and enters the hydrofining reaction zone, and then gas - liquid separation is carried out to obtain a gas - phase stream and a liquid - phase stream; control the nitrogen content in the liquid - phase stream in step (1);

[0065] (2) In the presence of hydrogen, the liquid - phase stream obtained in step (1) sequentially enters the first hydrocracking reaction zone and the second hydrocracking reaction zone; the first hydrocracking reaction zone is filled with the first hydrocracking catalyst; the second hydrocracking reaction zone is filled with the second hydrocracking catalyst; and control the content of C7 + n - paraffins in the effluent of the first hydrocracking reaction;

[0066] (3) The effluent of the second hydrocracking reaction in step (2) is separated and fractionated to obtain a gas fraction, light naphtha, heavy naphtha, and tail oil, and the tail oil is recycled to the second hydrocracking reaction zone.

[0067] The specific process conditions and hydrocracking effects are shown in Table 5.

[0068] Comparative Example 1

[0069] The difference from Example 1 is that after hydrofining, the feedstock directly enters the second hydrocracking reaction zone and reacts with the Cat - B1 catalyst.

[0070] The process conditions and hydrocracking effects in this example are shown in Table 5.

[0071] Comparative Example 2

[0072] The difference from Example 1 is that in step (1), the content of C7 + n - paraffins in the effluent of the first hydrocracking reaction is controlled to be 4%.

[0073] The process conditions and hydrocracking effects in this example are shown in Table 5.

[0074] Comparative Example 3

[0075] The difference from Example 1 is that catalyst Cat-B2 is loaded in the first hydrocracking reaction zone.

[0076] In this example, the process conditions and the hydrotreating effect are shown in Table 5.

[0077] Comparative Example 4

[0078] The difference from Example 1 is that catalyst Cat-B1 is loaded in the first hydrocracking reaction zone.

[0079] In this example, the process conditions and the hydrotreating effect are shown in Table 5.

[0080] Comparative Example 5

[0081] The difference from Example 1 is that the nitrogen content in the liquid-phase stream described in Step (1) is controlled to be 200 mg / kg. In this example, the process conditions and the hydrotreating effect are shown in Table 5.

[0082] Table 1 Physicochemical properties of the first hydrocracking catalyst

[0083] Catalyst Cat-A1 Cat-A2 Cat-A3 <![CDATA[Pore volume, cm 3 / g]]> 0.35 0.45 0.25 <![CDATA[Specific surface area, m 2 / g]]> 300 200 400 Content, wt%, based on the weight of the support ZSM-5 58 42 85 Aluminum oxide 42 58 15 Active metal content in the catalyst, wt% <![CDATA[MoO3]]> 10.0 15.0 5.0 NiO 3.5 2.0 5.0 Support content, wt% 86.5 83.0 90.0 <![CDATA[SiO2 / Al2O3 molar ratio of ZSM-5]]> 40 60 20

[0084] Table 2 Physicochemical properties of the second hydrocracking catalyst

[0085] Catalyst properties Cat-B1 Cat-B2 <![CDATA[Pore volume, cm 3 / g]]> 0.35 0.35 <![CDATA[Specific surface area, m 2 / g]]> 300 300 Catalyst composition Beta, wt% 50 - Y, wt% - 50 <![CDATA[MoO3, wt%]]> 10 10 NiO, wt% 5 5 Aluminum oxide, wt% 35 35

[0086] Table 3 Physicochemical properties of the hydrofining catalyst

[0087] Catalyst properties Cat-D <![CDATA[Pore volume, cm 3 / g]]> 0.35 <![CDATA[Specific surface area, m 2 / g]]> 300 Catalyst composition <![CDATA[MoO3, wt%]]> 25 NiO, wt% 5 Aluminum oxide support, wt% 70

[0088] Table 4 Main properties of the feedstock

[0089] Name of feedstock Heavy distillate oil <![CDATA[Density (20 °C), g / cm -3 > 0.8933 Distillation range / °C (ASTM D86) IBP / 10% 167 / 248 30％ / 50％ 316 / 374 70％ / 90％ 428 / 501 95% / EBP - / 663 Normal paraffin, wt% 18 Cyclic hydrocarbon, wt% 71 Nitrogen content, wt% 1.09 Oxygen content, wt% 0.85

[0090] Table 5 Hydrotreating effect

[0091]

[0092]

[0093] Continued Table 5

[0094]

[0095]

[0096] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A hydrocracking method for heavy distillate oil, which uses heavy distillate oil as raw material to produce chemical raw materials by hydrocracking, wherein, The method includes: (1) A heavy fraction oil is mixed with hydrogen and enters a hydrofining reaction zone, and then gas-liquid separation is carried out to obtain a gas-phase stream and a liquid-phase stream; the nitrogen content in the liquid-phase stream in step (1) is controlled to be 50 mg / kg to 100 mg / kg; (2) In the presence of hydrogen, the liquid-phase stream obtained in step (1) enters the first hydrocracking reaction zone to selectively crack the n-alkanes in the heavy distillate oil feedstock, obtaining a first hydrocracking product; wherein, in the first hydrocracking product, the mass content of C7 + n-alkanes is controlled to be below 3.0%; (3) In the presence of hydrogen, the first hydrocracking product enters a second hydrocracking reaction zone to obtain a second hydrocracking product containing monocyclic cyclic hydrocarbons; (4) The second hydrocracking product is separated and fractionated to obtain a gas fraction, light naphtha, heavy naphtha, and tail oil; In step (2), the first hydrocracking reaction zone is filled with a first hydrocracking catalyst; the first hydrocracking catalyst includes an active metal component and a carrier; the carrier includes one or more of ZSM-5 zeolite, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35, and ZSM-38 zeolites; For the first hydrocracking catalyst, based on the weight of the catalyst, the content of the carrier is 80.0% to 93.0%; in the carrier of the first hydrocracking catalyst, based on the weight of the carrier, the content of the zeolite is 40% to 92%; In step (3), the second hydrocracking reaction zone is filled with a second hydrocracking catalyst; the second hydrocracking catalyst includes a cracking component, a hydrogenation component, and a binder; In step (3), in the second hydrocracking reaction zone, a catalyst with Y zeolite as the cracking component and a catalyst with Beta zeolite as the cracking component are filled in sequence along the direction of the material flow; For the second hydrocracking catalyst, based on the weight of the second hydrocracking catalyst, the content of the hydrogenation component calculated as an oxide is 5 wt% to 40 wt%; the content of the cracking component is 20 wt% to 80 wt%; the content of the binder is 5 wt% to 75 wt%; The chemical raw materials include ethane, propane, butane, light naphtha, and heavy naphtha. Among them, heavy naphtha is used as a reforming raw material to produce BTX; ethane, propane, butane, and light naphtha are used as ethylene raw materials to produce low-carbon olefins; in the obtained chemical raw materials, based on the total mass of ethane, propane, butane, and light naphtha, the normal paraffins account for 54% to 70%; In the heavy fraction oil, the mass content of cyclic hydrocarbons is 40% to 90%, where the cyclic hydrocarbons are the sum of naphthenes and aromatics, and the mass content of normal paraffins is 5% to 50%.

2. The method according to claim 1, characterized in that, Control the nitrogen content in the liquid-phase stream in step (1) to be 60 mg / kg to 80 mg / kg.

3. The method according to claim 1, characterized in that, In the heavy fraction oil in step (1), the mass content of normal paraffins is 10% to 30%.

4. The method according to claim 1, wherein In the heavy fraction oil in step (1), the heavy fraction oil is at least one of coal tar and shale oil.

5. The method according to claim 1, wherein The reaction conditions in the hydrofining reaction zone in step (1) are as follows: the reaction pressure is 16 - 22 MPa; the average reaction temperature is 250 - 450 °C; the liquid hourly space velocity is 0.1 - 15.0 h -1 ; the hydrogen-oil volume ratio is 100:1 - 2500:

1.

6. The method according to claim 1, wherein The reaction conditions in the hydrofining reaction zone in step (1) are as follows: the average reaction temperature is 300~400°C; the liquid hourly space velocity is 0.5~5.0 h -1 ; the hydrogen-oil volume ratio is 400:1~2000:

1.

7. The method according to claim 1, wherein Control C7 in step (2) + The mass content of the n-alkane is 1 wt% to 3 wt%.

8. The method according to claim 1, wherein In the first hydrocracking product of step (2), the ratio of the mass of C6-C8 monocyclic cyclic hydrocarbons to the total mass of cyclic hydrocarbons in the raw material is 0.15 to 0.

35.

9. The method according to claim 8, wherein In the first hydrocracking product of step (2), the ratio of the mass of C6-C8 monocyclic cyclic hydrocarbons to the total mass of cyclic hydrocarbons in the raw material is 0.25 to 0.

34.

10. The method according to claim 1, wherein The zeolite of the first hydrocracking catalyst in step (2) is ZSM-5 zeolite.

11. The method according to claim 10, wherein The specific surface area of the first hydrocracking catalyst is 200~400m 2 / g, and the pore volume is 0.25~0.45mL / g.

12. The method according to claim 1, wherein The reaction conditions in the first hydrocracking reaction zone in step (2) are as follows: the reaction pressure is 16 - 22 MPa; the average reaction temperature is 250 - 450 °C; the liquid hourly space velocity is 0.1 - 15.0 h -1 ; the hydrogen-oil volume ratio is 100:1 - 2500:

1.

13. The method according to claim 12, characterized in that, The reaction conditions in the first hydrocracking reaction zone in step (2) are as follows: the average reaction temperature is 300~400°C; the liquid hourly space velocity is 1.0~5.0 h -1 ; the hydrogen-oil volume ratio is 400:1~2000:

1.

14. The method according to claim 1, wherein In step (3), the volume ratio of the catalyst with Y zeolite as the cracking component to the catalyst with Beta zeolite as the cracking component is 1:1 to 1:

5.

15. The method according to claim 14, wherein In step (3), the volume ratio of the catalyst with Y zeolite as the cracking component to the catalyst with Beta zeolite as the cracking component is 1:2 to 1:

4.

16. The method according to claim 1, wherein In step (3), the reaction conditions in the second hydrocracking reaction zone are as follows: the reaction pressure is 16 - 22 MPa; the average reaction temperature is 250 - 450 °C; the liquid hourly space velocity is 0.1 - 15.0 h -1 ; the hydrogen-to-oil volume ratio is 100:1 - 2500:

1.

17. The method according to claim 16, wherein In step (3), the reaction conditions in the second hydrocracking reaction zone are as follows: the average reaction temperature is 300~400°C; the liquid hourly space velocity is 1.0~5.0 h -1 ; the hydrogen-oil volume ratio is 400:1~2000:

1.

18. The method according to claim 1, characterized in that, The hydrofining reaction zone, the first hydrocracking reaction zone, and the second hydrocracking reaction zone adopt the same pressure.

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